$prefix = '.mar'


for $num in (1..5)
  {$prefix}-l__{$num*15}  
    margin-left: $num*15px

for $num in (1..5)
  {$prefix}-r__{$num*15}  
    margin-right: $num*15px

for $num in (1..5)
  {$prefix}-t__{$num*15}  
    margin-top: $num*15px

for $num in (1..5)
  {$prefix}-b__{$num*15}  
    margin-bottom: $num*15px